// A circular queue.
class CircularQueue implements ICharQ {
  private char q[]; // this array holds the queue
  private int putloc, getloc; // the put and get indices

  // Construct an empty queue given its size.
  public CircularQueue(int size) {
    q = new char[size+1]; // allocate memory for queue
    putloc = getloc = 0;
  }

  // Put a characer into the queue.
  public void put(char ch) {
    /* Queue is full if either putloc is one less than
       getloc, or if putloc is at the end of the array
       and getloc is at the beginning. */
    if(putloc+1==getloc |
       ((putloc==q.length-1) & (getloc==0))) {
      System.out.println(" -- Queue is full.");
      return;
    }

    q[putloc++] = ch;
    if(putloc==q.length) putloc = 0; // loop back

  }

  // Get a character from the queue.
  public char get() {
    if(getloc == putloc) {
      System.out.println(" -- Queue is empty.");
      return (char) 0;
    }

    char ch = q[getloc++];
    if(getloc==q.length) getloc = 0; // loop back
    return ch;
  }
}